Modern processors include multiple instances of processor cores that can be turned on or off independently as directed by a Power Control Unit (PCU). A multi-core processor, for example, is a single computing component with two or more independent actual central processing units (also referred to as “functional units,” “cores” or “processor cores”), which are the units that read and execute program instructions. The instructions are typically CPU instructions, but multiple cores can run multiple instructions at the same time, increasing overall speed for programs amenable to parallel computing. Manufacturers typically integrate the cores onto a single integrated circuit die, or onto multiple dies in a single package. A dual-core processor has two cores, a quad-core processor has four cores, and so on. Homogenous multi-core systems include only identical cores, and heterogeneous multi-core systems have cores that are not identical. Cores on conventional heterogeneous multi-core systems operate at the same frequency.